xii CHURCH OF S. JOHN THE BAPTIST IN TRULLO 205 barrel vaults3 and the walls are pierced by triple windows. Two capitals built into the exterior face of the northern wall, and marked with a cross3 were doubtless the capitals of the shafts which divided the northern window into three lights. The western arm of the cross is covered by the roof of the narthex? and lighted by a small round-headed window above It. The small narthex is In three bayss covered with cross-groined vaults. It is not probable that the church was converted into a mosque before 15913 when the patriarchal seat was removed from the Pammakaristos to S. Demetrius beside the Xylo-porta. Nor could the conversion have been later than 15983 the year In which Achmed Pasha—who converted the building into a mosque—died.1 1 Cf. Paspatesj p. 304.